The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Haruyuki Minamitani - One of the best experts on this subject based on the ideXlab platform.
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direct measurement of erythrocyte Deformability in diabetes mellitus with a transparent microchannel capillary model and high speed video camera system
Microvascular Research, 2001Co-Authors: Kosuke Tsukada, Eiichi Sekizuka, Chikara Oshio, Haruyuki MinamitaniAbstract:To measure erythrocyte Deformability in vitro, we made transparent microchannels on a crystal substrate as a capillary model. We observed axisymmetrically deformed erythrocytes and defined a deformation index directly from individual flowing erythrocytes. By appropriate choice of channel width and erythrocyte velocity, we could observe erythrocytes deforming to a parachute-like shape similar to that occurring in capillaries. The flowing erythrocytes magnified 200-fold through microscopy were recorded with an image-intensified high-speed video camera system. The sensitivity of Deformability measurement was confirmed by comparing the deformation index in healthy controls with erythrocytes whose membranes were hardened by glutaraldehyde. We confirmed that the crystal microchannel system is a valuable tool for erythrocyte Deformability measurement. Microangiopathy is a characteristic complication of diabetes mellitus. A decrease in erythrocyte Deformability may be part of the cause of this complication. In order to identify the difference in erythrocyte Deformability between control and diabetic erythrocytes, we measured erythrocyte Deformability using transparent crystal microchannels and a high-speed video camera system. The Deformability of diabetic erythrocytes was indeed measurably lower than that of erythrocytes in healthy controls. This result suggests that impaired Deformability in diabetic erythrocytes can cause altered viscosity and increase the shear stress on the microvessel wall.
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The automatic image analysis of red blood cell Deformability and blood flow in microchannels with an image-intensified high-speed video camera system
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards, 1998Co-Authors: T. Shimizu, Eiichi Sekizuka, Chikara Oshio, K. Tsukada, T. Nagai, R. Hokari, Haruyuki MinamitaniAbstract:It is crucial in microcirculatory investigation to evaluate red blood cell (RBC) Deformability. However, there are almost limited information and indirect method of analyses. The authors tried to measure RBC Deformability automatically by a combination of a newly developed algorithm and recording of individual RBC images clearly with an image-intensified high-speed video camera system. The length and the diameter of individual RBCs were measured automatically for RBC velocity measurement. RBC Deformability was calculated from the histogram of density at each pixel by the authors' algorithm. To ensure reliability of this system the authors compared actual measurement with automatic analysis for RBC velocity and RBC Deformability. Each correlation value (R/sup 2/=0.99) showed the validity of this system. In addition this system can shorten the time needed for measuring. The authors could confirm that the Deformability of diabetic RBCs of HbAlc 12.1% was much more decreased compared with that of Hbalc 6.4%. The Deformability of diabetic RBCs might depend on hyperglycemic degree of diabetic patients. In addition, the pentoxifylline improved the Deformability of diabetic RBCs.
Philippe Connes - One of the best experts on this subject based on the ideXlab platform.
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Impact of surface-area-to-volume ratio, internal viscosity and membrane viscoelasticity on red blood cell Deformability measured in isotonic condition
Scientific Reports, 2019Co-Authors: Céline Renoux, Magalie Faivre, Amel Bessaa, Lydie Da Costa, Philippe Joly, Alexandra Gauthier, Philippe ConnesAbstract:osmotic gradient ektacytometry is the gold standard to assess red blood cell (RBC) Deformability. It has been proposed that, when measured in isotonic condition, RBC Deformability at low shear stress would depend on membrane elasticity while it would be influenced by internal viscosity when measured at high shear stress, but this hypothesis needs to be further addressed. Healthy RBCs were rigidified by treatment with lysolecithine (LpC), diamide or nystatine associated with hyperosmolar solutions (osMo), which reduces membrane surface area, decreases membrane elasticity or promotes cell dehydration, respectively. Diamide treatment resulted in a decrease in isotonic RBC Deformability at all shear stresses tested (i.e. from 0.3 to 30 Pa). LPC and OSMO treatments caused a decrease in isotonic RBC Deformability above 3 Pa only. Isotonic RBC Deformability from patients with hereditary spherocytosis or sickle cell disease was mainly decreased above 1.69 Pa. Our findings indicate that decreased isotonic RBC Deformability at shear stresses above 3 Pa would be related to a reduction in the surface-area-to-volume ratio and/or to a loss of membrane elasticity and/or to an increase in internal viscosity while a decrease of RBC Deformability below 3 Pa would reflect a loss of membrane elasticity.
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Indirect viscosimetric method is less accurate than ektacytometry for the measurement of red blood cell Deformability.
Clinical Hemorheology and Microcirculation, 2018Co-Authors: Jens Vent-schmidt, Xavier Waltz, Aurélien Pichon, Marie-dominique Hardy-dessources, Marc Romana, Philippe ConnesAbstract:The aim of this study was to test the accuracy of viscosimetric method to estimate the red blood cell (RBC) Deformability properties. Thirty-three subjects were enrolled in this study: 6 healthy subjects (AA), 11 patients with sickle cell-hemoglobin C disease (SC) and 16 patients with sickle cell anemia (SS). Two methods were used to assess RBC Deformability: 1) indirect viscosimetric method and 2) ektacytometry. The indirect viscosimetric method was based on the Dintenfass equation where blood viscosity, plasma viscosity and hematocrit are measured and used to calculate an index of RBC rigidity (Tk index). The RBC Deformability/rigidity of the three groups was compared using the two methods. Tk index was not different between SS and SC patients and the two groups had higher values than AA group. When ektacytometry was used, RBC Deformability was lower in SS and SC groups compared to the AA group and SS and SC patients were different. Although the two measures of RBC Deformability were correlated, the association was not very high. Bland and Altman analysis demonstrated a 3.25 bias suggesting a slight difference between the two methods. In addition, the limit of agreement represented 28% (>15%) of the mean values of RBC Deformability, showing no interchangeability between the two methods. In conclusion, measuring RBC Deformability by indirect viscosimetry is less accurate than by ektacytometry, which is considered the gold standard.
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red blood cell nitric oxide synthase modulates red blood cell Deformability in sickle cell anemia
Clinical Hemorheology and Microcirculation, 2016Co-Authors: Philippe Connes, Marc Romana, Anais Mozar, Bianca Collins, Mariedominique HardydessourcesAbstract:Sickle cell anemia (SCA) is an inherited red blood cells (RBC) disorder characterized by significantly decreased RBC Deformability. The present study aimed to assess whether modulation of RBC Nitric Oxide Synthase (RBC-NOS) activation could affect RBC Deformability in SCA.Blood of twenty-five SCA patients was treated for 1 hour at 37°C with Phosphate Buffered Saline (PBS) or PBS containing 1% of Dimethylsulfoxyde as control, L-arginine or N(5)-(1-Iminoethyl)-L-ornithine (L-NIO) to directly stimulate or inhibit RBC-NOS, insulin or wortmannin to indirectly stimulate or inhibit RBC-NOS through their effects on the PI3 Kinase/Akt pathway, and sodium nitroprusside (SNP) and 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) as NO donor and NO scavenger, respectively. RBC Deformability was measured by ektacytometry at 3 Pa.RBC Deformability significantly increased after insulin treatment and significantly decreased after L-NIO and wortmannin incubation. The other conditions did not affect Deformability. Significantly increased nitrotyrosine levels, a marker of enhanced free radical generation, were detected by immunohistochemistry in SNP and insulin treated samples.These data suggest that RBC Deformability of SCA can be modulated by RBC-NOS activity but also that oxidative stress may impair effectiveness of RBC-NOS produced NO.
Oguz K. Baskurt - One of the best experts on this subject based on the ideXlab platform.
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the effect of alcohols on red blood cell mechanical properties and membrane fluidity depends on their molecular size
PLOS ONE, 2013Co-Authors: Melda Sonmez, Ozlem Yalcin, Huseyin Yavuz Ince, Vladimir Ajdžanovic, Ivan Spasojevic, Herbert J Meiselman, Oguz K. BaskurtAbstract:The role of membrane fluidity in determining red blood cell (RBC) Deformability has been suggested by a number of studies. The present investigation evaluated alterations of RBC membrane fluidity, Deformability and stability in the presence of four linear alcohols (methanol, ethanol, propanol and butanol) using ektacytometry and electron paramagnetic resonance (EPR) spectroscopy. All alcohols had a biphasic effect on Deformability such that it increased then decreased with increasing concentration; the critical concentration for reversal was an inverse function of molecular size. EPR results showed biphasic changes of near-surface fluidity (i.e., increase then decrease) and a decreased fluidity of the lipid core; rank order of effectiveness was butanol > propanol > ethanol > methanol, with a significant correlation between near-surface fluidity and Deformability (r = 0.697; p<0.01). The presence of alcohol enhanced the impairment of RBC Deformability caused by subjecting cells to 100 Pa shear stress for 300 s, with significant differences from control being observed at higher concentrations of all four alcohols. The level of hemolysis was dependent on molecular size and concentration, whereas echinocytic shape transformation (i.e., biconcave disc to crenated morphology) was observed only for ethanol and propanol. These results are in accordance with available data obtained on model membranes. They document the presence of mechanical links between RBC Deformability and near-surface membrane fluidity, chain length-dependence of the ability of alcohols to alter RBC mechanical behavior, and the biphasic response of RBC Deformability and near-surface membrane fluidity to increasing alcohol concentrations.
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effect of hemoglobin oxygenation level on red blood cell Deformability and aggregation parameters
Clinical Hemorheology and Microcirculation, 2009Co-Authors: Mehmet Uyuklu, Herbert J Meiselman, Oguz K. BaskurtAbstract:;. Measurements of red blood cell (RBC) Deformability and aggregation can be subject to influence by pre-analytical handling procedures, with the degree of hemoglobin oxygenation having the potential to affect the results. To examine such effects, RBC Deformability and aggregation were studied before and after oxygenation or deoxygenation of human blood samples. RBC Deformability was assessed using a laser-diffraction ektacytometer having Couette geometry. RBC aggregation was assessed using the same system by monitoring light backscattering after a sudden cessation of high shear; aggregation was also measured by monitoring light transmittance through RBC suspensions. RBC Deformability was found to be significantly increased after equilibrating RBC with ambient air (pO 2 : 142.0 ± 3.1 mmHg) compared to the non-oxygenated sample (pO 2 : 42.4 ± 1.8 mmHg). In contrast, equilibration with 100% nitrogen resulted in significant impairment in RBC Deformability. RBC aggregation parameters were also affected by oxygenation if measured based on light backscattering, but not if measured using light transmittance. It is thus recommended that blood samples be oxygenated by repeated exposure to ambient air prior to the measurement of hemorheological parameters.
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Effect of sulfite on red blood cell Deformability ex vivo and in normal and sulfite oxidase-deficient rats in vivo
Archives of toxicology, 2005Co-Authors: Melek Bor-kucukatay, Vural Kucukatay, Aysel Agar, Oguz K. BaskurtAbstract:The effect of sulfite, a widely used food additive, on red blood cell Deformability ex vivo and in vivo was investigated. Ex vivo experiments were conducted in human blood exposed to sulfite (5, 10 and 20 mM). In vivo experiments were carried out in sulfite oxidase-competent (SOXC) and sulfite oxidase-deficient (SOXD) rats. In the in vivo experiments, sulfite was administered in the form of sodium metabisulfite (Na2S2O5, 25 mg/kg/day) via drinking water. Vitamin E dissolved in olive oil at a dose of 50 mg/kg was administered by gastric gavages. Red blood cell (RBC) Deformability was determined at various fluid shear stresses using an ektacytometer. Ex vivo sulfite exposure to RBC did not affect RBC Deformability. In the in vivo experiments, although RBC Deformability was not affected by sulfite treatment in SOXD rats, it was found to be significantly increased in SOXC rats. Vitamin E treatment in combination with sulfite caused impairment in RBC Deformability in both SOXC and SOXD rats. We suggest that sulfite needs to be oxidized in order to improve RBC Deformability.
Kosuke Tsukada - One of the best experts on this subject based on the ideXlab platform.
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direct measurement of erythrocyte Deformability in diabetes mellitus with a transparent microchannel capillary model and high speed video camera system
Microvascular Research, 2001Co-Authors: Kosuke Tsukada, Eiichi Sekizuka, Chikara Oshio, Haruyuki MinamitaniAbstract:To measure erythrocyte Deformability in vitro, we made transparent microchannels on a crystal substrate as a capillary model. We observed axisymmetrically deformed erythrocytes and defined a deformation index directly from individual flowing erythrocytes. By appropriate choice of channel width and erythrocyte velocity, we could observe erythrocytes deforming to a parachute-like shape similar to that occurring in capillaries. The flowing erythrocytes magnified 200-fold through microscopy were recorded with an image-intensified high-speed video camera system. The sensitivity of Deformability measurement was confirmed by comparing the deformation index in healthy controls with erythrocytes whose membranes were hardened by glutaraldehyde. We confirmed that the crystal microchannel system is a valuable tool for erythrocyte Deformability measurement. Microangiopathy is a characteristic complication of diabetes mellitus. A decrease in erythrocyte Deformability may be part of the cause of this complication. In order to identify the difference in erythrocyte Deformability between control and diabetic erythrocytes, we measured erythrocyte Deformability using transparent crystal microchannels and a high-speed video camera system. The Deformability of diabetic erythrocytes was indeed measurably lower than that of erythrocytes in healthy controls. This result suggests that impaired Deformability in diabetic erythrocytes can cause altered viscosity and increase the shear stress on the microvessel wall.
Andrew W Steiner - One of the best experts on this subject based on the ideXlab platform.
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tidal Deformability with sharp phase transitions in binary neutron stars
Physical Review D, 2019Co-Authors: Sophia Han, Andrew W SteinerAbstract:The neutron star tidal Deformability is a critical parameter which determines the premerger gravitational-wave signal in a neutron star merger. In this article, we show how neutron star tidal deformabilities behave in the presence of one or two sharp phase transition(s). We characterize how the tidal Deformability changes when the properties of these phase transitions are modified in dense matter equations of state. Sharp phase transitions lead to the smallest possible tidal deformabilities and also induce discontinuities in the relation between tidal Deformability and gravitational mass. These results are qualitatively unmodified by a modest softening of the phase transition. Finally, we test two universal relations involving the tidal Deformability and show that their accuracy is limited by sharp phase transitions.
